Austenitic manganese steels containing 10 to 14% manganese are frequently used to resist wear from severe impact and moderate abrasion in many industrial applications such as: rail crossovers; frogs and switchpoints; crusher hammers; dredge parts; rolling mill parts; drive sprockets, and the like. In such applications, the wear surface usually is provided either by: welding a plate or part of this high manganese containing steel to a plain carbon or low alloy steel structure; by hardfacing a worn surface using a high manganese containing electrode; or by rebuilding the structure by removing the worn surface and welding a new part of high manganese steel in its place.
In either case, an electrode is employed comprised of a tube of low carbon steel with the inside filled with various known fluxing ingredients to give a smooth arc, minimum spatter and operator appeal, and alloying ingredients, primarily large amounts of manganese, and lesser amounts of nickel, chromium and carbon, all in amounts and ratios which will produce the desired optimum alloy content in the deposited weld bead.
While hardness and abrasion resistance are of the utmost importance, the ability to weld one high manganese containing steel to another piece of high manganese containing steel, or to a piece of plain carbon or low alloy steel without cracking is likewise important. Thus, in one instance, in the prior art, one manufacturer supplied one electrode for hardsurfacing and another electrode for the welding of a high manganese containing steel part to a plain carbon or low alloy steel part. In the alternative, it is the practice to sacrifice abrasion resistance in the weld bead for the ability to also weld the high manganese containing steel to plain carbon or low alloy steel parts without cracking using the same electrode.
A third approach taken in prior art electrodes is to sacrifice arc action and welding characteristics to obtain crack resistance at the desired abrasion resistance level. This compromise is made by using a slag system containing little or no TiO.sub.2. This results in a very low titanium residual in the weld deposit which minimizes cracking at the carbon levels necessary for good abrasion resistance. The welding characteristics of this system, however, are undesirable due to a very globular type of metal transfer that produces high metal spatter levels, poor weld bead surface appearance, and narrower bead profiles that do not permit a smooth tie-in to adjacent weld beads.
A further problem in the design of electrodes for producing the high abrasion resistant welds or weld surfaces is in the cost of the alloying ingredients. Large amounts of alloys are employed and it is desirable to produce the high abrasion resistance at a minimum cost. This requires using the minimum amount of total fill in the electrode along with alloying ingredients in a low cost form.
In the design of a high manganese electrode, it is conventional to test the abrasion resistance by subjecting identical specimens of 0.30% carbon steel and of the high manganese containing steel to an identical abrasion test consisting of pressing the specimens against a slowly rotating, water cooled grinding wheel under relatively high pressure for predetermined identical periods of time and measuring the amount of metal abraded away from each specimen. The abrasion resistance rating is then determined by dividing the amount of metal removed from the 0.30% carbon steel specimen by the amount of metal removed from the high manganese containing specimen. Heretofore an abrasion resistance rating of 5 to 7 times that of 0.30% carbon steel was considered satisfactory.